The present invention relates to a tracked vehicle as recited in the preamble to claim 1.
Tracked vehicles of this type are known not only for civilian applications, as construction machinery for example, but also in the military, as armored combat vehicles for example.
A tracked vehicle of the present type features as a rule two lateral tracks mounted around a wheelset and separately driven by drive wheels. Each drive wheel is part of a drive unit associated with each track. Each drive unit also includes an electric motor, a drive train upstream of the drive wheel, and a shaft that drivingly connects the electric motor to the drive train. The drive units and the wheelset is mounted directly against the vehicle""s pan, the electric motors on its inner surface and the chain drives on its outer surface. The shaft extends through the vehicle pan and drives the drive train, a planetary gear. The drive train drives the drive wheels, and the drive wheels the tracks. The drive train is mounted directly to the outer surface of the vehicle pan.
There are problems with this embodiment. The drive mechanisms can cause vibrations in the tracks. Irregularities in the terrain can also lead to such vibrations, that can be transmitted to the wheelset and drive wheels and eventually to the vehicle pan. The vibrations can seriously disturb the driver and crew by subjecting them to constant jolting.
The vibrations can also severely damage the optical devices in an armored combat vehicle.
The situation is aggravated because, since the electric motor is part of a drive unit, the stator must be as close as possible to the rotor to ensure high efficiency. Since, however, the vibrations are induced directly into the rotor and transmitted to the stator, the electric motor can fail when the stator and rotor do not vibrate synchronized but interfere with each other.
Bearing for another design of tracked vehicle is known from generic German 2 555 021 A. In this system a track drive wheel and a drive train are accommodated in one of the vehicle pan""s walls. Another drive train is accommodated separately along with a drive unit inside the vehicle pan and are connected by a universal shaft. There is a drawback to this system in that vibrations can also be transmitted into the vehicle pan by way of shaft, the drive train, and the drive unit. Furthermore, the drive mechanism is very rigid and takes up a lot of room inside the vehicle. This tracked vehicle is to this extent of a different type.
The object of the present invention is accordingly to improve a tracked vehicle of the type recited in the preamble to claim 1 to the extent that it will not have the aforesaid drawbacks and that vibrations induced in the drive wheels by way of the tracks will not be transmitted to the vehicle pan.
This object is attained in accordance with the present invention in a tracked vehicle of the aforesaid type by the characteristics recited in the body of claim 1.
The present invention derives from the awareness that vibrationally separating the drive unit comprising the drive wheel, drive train, shaft, and electric motor from the assembly""s accommodation, specifically the vehicle pan, will allow simple means of preventing drive train of the vibrations.
Means of damping vibrations are accordingly interposed in accordance with the present invention between the walls of the vehicle pan and the drive unit, vibrationally separating them.
The vibration-damping means in one embodiment are mounted on one surface of the walls, specifically on either the outer surface or the inner surface. To run the tracks as close to the walls of the vehicle pan as possible for example, the vibration-damping means will be mounted on their inner surface, allowing some of the drive unit to be installed inside the vehicle pan. If on the other hand it is desired to provide as much space as possible inside the vehicle pan, it will be of benefit to mount the vibration-damping means on the outer surface. The whole drive unit can in this event be accommodated outside the vehicle pan.
The vibration-damping means can as an alternative be mounted on both the inner surface and the outer surface. This approach will allow part of the drive unit to be accommodate inside the vehicle pan and part outside. The vibration-damping means can then be fine-tuned to the particular vibrations that occur, the interior means being provided with a damping factor that differs from that of the exterior means.
The drive train and the electric motor in each drive unit can each be provided with a static component and a rotating component. Either the static component of the drive train or the static component of the electric motor or both are connected to the vibration-damping means.
In one embodiment the static component of the electric motor is connected to the vibration-damping means on the inner surface and the static component of the drive train to the vibration-damping means on the outer surface of the walls of the vehicle pan. This arrangement allows early vibration damping and prevents drive train of the vibrations into the drive unit.
The static components of the electric motors and drive trains in one embodiment are rigidly interconnected, at least one static component connected to the walls by way of vibration-damping means. This approach provides a simple means of preventing relative motions on the part of the static components and hence of the rotating components as well.
The static components of the drive train and of the electric motor can alternatively be connected by way of means of transmitting torque, allowing compensation of radial and axial motions of the static components relative to each other. Such relative motions sometimes occur in operation as the result of sudden stress on the tracks due to irregularities in the terrain.
For particular applications it may be necessary to accommodate the electric motor on one side and either the drive wheel or the drive train on the other as far apart as possible.
In this event it will be of advantage to provide one or more particularly loosely accommodated components to rigidly connect the static components of the electric motor and of the drive train and to span the distance between them.
The components that span the distance can in particular be part of the static component of the electric motor and/or the drive train.
To prevent the rotating components from jamming, the shaft of the drive unit is connected to the rotating component of the electric motor and/or to the rotating component of the drive train by means for compensating radial and axial motions of the shaft relative to the rotating component of the electric motor and of the drive train.
This arrangement will protect the electric motor, which as hereinbefore described has a narrow gap between its rotor and stator, between, that is, its rotating component and its static component.
The drive train in one embodiment of the present invention includes a planetary gear, the shaft of the drive unit constituting the shaft of a sunwheel in the planetary gear. This arrangement allows immediate drive train of forces and decreases the number of necessary components.
The range of possible embodiments can be extensively increased if the drive train comprises an axially offset drive train. Electric motors with long diameters can then be employed for example, in that it is well known that the diameter participates quadratically and the length of the electric motor or its coil linearly in torque. Electric motors with long diameters must accordingly be installed displaced from their ideal location due to the limited amount of space available, in armored combat vehicles in particular, a demand that is easily satisfied when the drive train is axially offset.
Assembly can be facilitated when the axially offset drive train and the electric motor constitute a single module.
To protect the vehicle pan and the sensitive equipment accommodated therein from vibrations, the vehicle""s wheelset can also be vibrationally uncoupled from the vehicle pan. Assembly can in this event be facilitated if at least some of the vibration-damping means in the drive unit and the wheelset constitute a single module.
One embodiment of the present invention features motion-limiting means that prevent large relative motions between the drive unit and the walls of the vehicle pan.
To expand the range of possible approaches to accommodating the drive unit in the vehicle pan, the vehicle pan is provided with a cutout associated with part of the drive unit.
To protect it from exterior mechanical action, the electric motor can be entirely accommodated on one surface of the walls, especially on the inner surface.
It will be of advantage for the same reason for the drive train to extend at least partly into the vehicle pan.